A panoramic photograph is a photograph with an unusually large field of view, an exaggerated aspect ratio, or both. High resolution panoramic photographs can be striking, especially when printed or displayed in a large size
Historically, panoramic photographs have been taken using specially-made cameras that produced negatives or transparencies of unusual sizes. Accordingly, panoramic photography was often practiced by professional photographers with specialized equipment for handling these unusual film sizes.
Another method of making a panoramic photograph is to take several overlapping conventional photographs, each typically having an aspect ratio of about 3:2, and then join them together into a single larger photograph. The joining is typically done using a computer operating on digital representations of the component photographs. Often, the digital representations are obtained directly using a digital camera to photograph the subject. This process of combining digital images into a larger photograph is often called stitching. Recent advances in computer hardware and software have enabled even amateur and casual photographers to create panoramic photographs by this method. Some digital cameras can perform stitching using an internal processor, without the need for a separate computer.
FIGS. 1A-1D illustrate the process of creating a panoramic photograph from component photographs. FIG. 1A shows a landscape scene 100 with a large field of view. FIG. 1B shows six overlapping component photographs 101, 102, 103, 104, 105, 106 of a conventional aspect ratio, taken so that each portion of scene 100 that is to be included in the resulting panoramic photograph is represented in at least one of the component photographs 101-106. FIG. 1C shows component photographs 101-106 in isolation. Certain features such as tree 107 and fence corner 108 appear in more than one of the component photographs, and may be used by the stitching process to align component photographs 101-106 with each other. FIG. 1D shows a stitched panoramic photograph 109 constructed by stitching component photographs 101-106 together. Stitched panoramic photograph 109 has a larger field of than any of component photographs 101-106. It might be possible to photograph the entire field of view of photograph 109 with a single exposure if a wide-angle lens were put on the camera, but that single wide-angle photograph would have less detail than stitched panoramic photograph 109.
A stitched panoramic photograph such as photograph 109 is sometimes called a “mosaic”. That term is sometimes used to describe a panoramic photograph stitched from a two-dimensional array of component photographs (such as example photograph 109), but for the purposes of this disclosure, the terms “stitched panoramic photograph” and “mosaic” will be used interchangeably to refer to a photograph stitched from an array of component photographs, whether the array consists of a single row or column, or comprises more than one row or column.
The component photographs used to create a mosaic may be individual still photographs, or may be frames of digital video. Often, when video frames are used, the interval between successive frames is short in relation to the speed of camera motion so that the fields of view of successive frames overlap considerably. Mathematical comparison of successive frames, for example using correlation techniques, can reveal information about the path of the camera motion. With sufficient processing capability, video stitching and motion tracking can be performed in real time.
Methods are well-known for stitching a mosaic from a suitable set of component photographs, and commercial software is available for performing this task. But camera users may struggle to take a suitable set of component photographs. In the absence of any guidance from the camera, the user must mentally keep track of how much of a scene is encompassed by a particular component photograph, and then properly position the camera for each succeeding component photograph so that the component photographs overlap, while avoiding excessive overlap. If an error is made and a portion of the scene is missed by all of the component photographs, the mosaic is ruined.
Some cameras provide a panoramic mode that assists the photographer in composing the component photographs, for example by indicating how much overlap exists between two consecutive photographs. However, these cameras typically do not provide assistance for composing two-dimensional mosaics, and typically require that the photographer take the leftmost component photograph of a stitched panorama first. This makes it difficult to estimate the correct position of the starting component photograph so that the ends of the stitched panorama are centered over the desired view. Furthermore, the camera may not provide a method of choosing exposure settings appropriate for the entire scene.